An oscillator more or less corresponding to the features set out above has already been described, by accident, in utility model DE 1789976 U, which relates to different alternative embodiments of an oscillator of the electromagnetic type. The embodiment of FIG. 2 relates to a pendulum comprising an arm whereof the free end bears a magnet intended to cooperate with reels to sustain the oscillations of the pendulum. The arm further bears an additional magnet, in its central part, intended to cooperate with a stationary magnet, the position of which is adjustable in reference to the frame of the clockwork movement, such that a fine adjustment of the specific frequency of the oscillations is made possible by modifying the position of the stationary magnet in reference to the trajectory of the magnet supported by the arm of the pendulum. This document sets out the possibility of implementing an alternative according to which this pendulum could theoretically oscillate in a sustained manner without the presence of the reels and therefore without the electromagnetic interaction sustaining the oscillations of the pendulum in the illustrated embodiment.
The present invention instead relates to the field of oscillators including a balance and intended to be implemented in a timepiece of the portable type, such as pocket watches or bracelet watches. The balance is generally associated with a balance-spring intended to lead to alternating return force moments to produce the oscillating movement.
Yet the manufacture of oscillators of the sprung balance type is delicate to master; in particular, producing the balance-springs requires very precise know-how that is not very widespread, which justifies the search for alternative solutions.
As an example, patent EP 1,805,565 B1 describes different embodiments of oscillators in which return forces are generated by one or several permanent magnets. More specifically, this document describes the construction of an oscillator including a balance or a pallet bearing at least one movable bipolar magnet associated with at least one stationary bipolar magnet, to generate return forces on the balance or on the pallet intended to act on an oscillating element, and in particular to reproduce the typical movement of a balance associated with a balance-spring, in the case of embodiments relative to balances. FIG. 11 shows an embodiment in which a small magnetized bar acts as a balance. This bar is arranged in a guide channel to perform a to-and-fro movement while being repelled on either side by the poles of a stationary permanent magnet. The cooperation mode of the magnetized bar with a pallet situated in a plane adjacent to that of the movements of the magnetized bar is not clearly specified and, overall, this embodiment appears to pertain more to a concept than a practical functional embodiment. The embodiment of FIG. 15 provides that the pallet itself bears two small permanent magnets arranged to cooperate with two stationary magnets to generate return forces on the pallet. Such a construction is supposed to lead to high-frequency oscillations of the pallet, for which it is probably difficult to ensure a good level of isochronism. In general, the embodiment proposed in this document breaks with the conventional constructions and require making significant changes to existing clockwork calibers to incorporate them.